根据百分比选择一个值

Question

我需要 select 一个基于该值被 select 编辑的概率百分比的值。例如：

10%的时间增量值a
20%的时间增量值b
30%的时间增量值c
40%的时间增量值d

百分比相加总是恰好为 100%

我遇到过几个类似this one的解决方案，但我确定它们不可能是正确的。这是使用提到的解决方案构建的示例程序：

import java.util.Random;

public class Main {

    private static Random r = new Random();

    public static void main(String[] args) {
        final int iterations = 1000000;
        System.out.println("Testing percentage based random, " + iterations + " iterations");
        int onePercent = 0;
        int sixPercent = 0;
        int sevenPercent = 0;
        int thirtySixPercent = 0;
        int fiftyPercent = 0;
        // Those values add up to 100% overall
        for (int i = 0; i < iterations; i++) {
            int random = r.nextInt(100);
            if (random < 1) {
                onePercent++;
                continue;
            }
            if (random < 6) {
                sixPercent++;
                continue;
            }
            if (random < 7) {
                sevenPercent++;
                continue;
            }
            if (random < 36) {
                thirtySixPercent++;
                continue;
            }
            if (random < 50) {
                fiftyPercent++;
                continue;
            }
            // That can't be right because if random > 50 then nothing at all happens
        }
        System.out.println("One percent happened about " + (onePercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Six percent happened about " + (sixPercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Seven percent happened about " + (sevenPercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Thirty six percent happened about " + (thirtySixPercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Fifty percent happened about " + (fiftyPercent / Float.valueOf(iterations)) * 100 + "% of the time");
    }
}

输出：

Testing percentage based random, 1000000 iterations
One percent happened about 0.99649996% of the time
Six percent happened about 4.9925% of the time
Seven percent happened about 1.0029999% of the time
Thirty six percent happened about 29.001299% of the time
Fifty percent happened about 14.0191% of the time

预期输出：

Testing percentage based random, 1000000 iterations
One percent happened about 0.99649996% of the time
Six percent happened about 6.9925% of the time
Seven percent happened about 7.0029999% of the time
Thirty six percent happened about 36.001299% of the time
Fifty percent happened about 50.0191% of the time

我认为我需要使用某种算法将百分比转换为从 0 到 99 的比例，以便随机数生成器可以准确地 select 一个值。不过我想不出该怎么做。

Answer 1

您的结果是正确的：

Fifty percent happened about 14.0191% of the time

50 - 36 = 14

Thirty six percent happened about 29.001299% of the time

36 - 7 = 29

Seven percent happened about 1.0029999% of the time

7 - 6 = 1

.....

删除所有 'continue' 语句，如果你想让它们总结。

Answer 2

想通了。您需要跟踪到目前为止测试的百分比并将其添加到当前测试中。

import java.util.Random;

public class Main {

    private static Random r = new Random();

    public static void main(String[] args) {
        final int iterations = 1000000;
        System.out.println("Testing percentage based random, " + iterations + " iterations");
        int onePercent = 0;
        int sixPercent = 0;
        int sevenPercent = 0;
        int thirtySixPercent = 0;
        int fiftyPercent = 0;
        // Those values add up to 100% overall
        for (int i = 0; i < iterations; i++) {
            int random = r.nextInt(100);
            int totalPercent = 0;
            if (random < totalPercent + 1) {
                onePercent++;
                continue;
            }
            totalPercent += 1;
            if (random < totalPercent + 6) {
                sixPercent++;
                continue;
            }
            totalPercent += 6;
            if (random < totalPercent + 7) {
                sevenPercent++;
                continue;
            }
            totalPercent += 7;
            if (random < totalPercent + 36) {
                thirtySixPercent++;
                continue;
            }
            totalPercent += 36;
            if (random < totalPercent + 50) {
                fiftyPercent++;
                continue;
            }
            totalPercent += 50;
            // That can't be right because if random > 50 then nothing at all happens
        }
        System.out.println("One percent happened about " + (onePercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Six percent happened about " + (sixPercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Seven percent happened about " + (sevenPercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Thirty six percent happened about " + (thirtySixPercent / Float.valueOf(iterations)) * 100 + "% of the time");
        System.out.println("Fifty percent happened about " + (fiftyPercent / Float.valueOf(iterations)) * 100 + "% of the time");
    }
}

根据百分比选择一个值

Selecting a value based on percentages

java

random

math

percentage